This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Coiled tubing is a technology that has been expanding its range of application since its introduction to the oil industry in the 1960's. Its ability to pass through completion tubulars and the wide array of tools and technologies that can be used in conjunction with it make it a very versatile technology.
In coiled tubing operations, the process whereby downhole tools are transferred from atmospheric pressure to wellbore pressure is called deployment. Most coiled tubing deployment is done using a riser long enough that the entire tool may be placed inside it at once, and then pressurized. However, for longer tools this is not feasible due to limitations on the maximum height for a coiled tubing injector. Charge pressure and crane availability may also present issues.
In such cases where longer tools are used, the tools are lowered into the well in sections and hung off of blow out preventer (BOP) rams using a deployment bar that matches the diameter of the coiled tubing. These sections are always placed in a riser and may be conveyed in by coiled tubing, wireline, or slickline. Failures are known to occur in this process when the precise order of steps is not followed. Failure usually consists of ejecting either wellbore fluids and/or the tool itself. This sort of failure is catastrophic, but it is usually possible to close the well in quickly using the BOP.
Inverted rams in BOPs are commonly used in wireline operations, and are most often used to contain grease injection between an inverted and regular wireline ram. The grease serves to seal the spaces present in armor wire strands of the wireline cable. These rams are also occasionally used to facilitate pressure testing by providing a way to deliver high pressure from the bottom of a BOP, independent of the well bore pressure. However, these rams add significant hazards when used, as they create a sealed cavity in the wellbore system above the BOP rams. If a ram is opened or closed in this cavity, the cavity pressure will either rise to dangerous levels or fall below well bore pressure which may lead to damage of the inverted ram or to the BOP itself.
One approach to obviate the above problems has been to protect inverted rams using a check valve incorporated in the BOP ram body to prevent reverse pressurization. However, this approach has not proven to be reliable.
Hence, it remains desirable to provide improvements in blow out preventer related equipment to protect internal rams and manage wellbore pressure, and the embodiments disclosed herein provide, at least in part, such improvement.